Probiotics are microbial organisms that are associated with beneficial health effects and may be used for the prevention and treatment of diseases. Lactic acid bacteria, such as bifidobacteria and lactobacilli, are probiotics that are beneficial in treating conditions such as diarrhea, food allergies, dental caries, and respiratory infections, and also find use as vaccine adjuvants.
When administered exogenously, probiotics can survive in sufficient numbers to affect gut microbial metabolism, although survival rates are limited to 20-40%. The main obstacles to probiotic survival in the gut include gastric acidity and the action of bile salts. Certain exogenously administered substances can enhance the action of both exogenous and endogenous probiotics. For instance, human milk can stimulate the growth of bifidobacteria in vitro and also in the small intestine of infants; however, it is unlikely that they function in the colon. Lactulose and certain fructose-containing compounds, called prebiotics, are not digested in the small intestine but pass into the colon unaltered, where they can be selectively utilized by probiotics. Beneficial effects may thus accrue from exogenously administered probiotics when administered with prebiotics. Oligofructose and other complex sugars such as oligoxylans, oligoarabinoxylans, and raffinose, however, cannot be metabolized by certain lactobacilli, and therefore, these prebiotics cannot support the growth of such organisms.
Lactobacillus is a type of lactic acid bacteria which is used to ferment milk products to produce yogurt, buttermilk, and cheeses. Lactobacilli are considered probiotics because of their health benefits and are generally recognized as safe (GRAS). The first systematic scientific investigations on the health benefits of Lactobacillus were conducted 100 years ago. The Lactobacillus rhamnosus strain GG (LGG; ATCC Accession No. 53103) is an optimal probiotic strain because of its ability to survive stomach acid and bile, and proceed intact to the intestines. LGG has been shown to be beneficial in treating a number of medical conditions including acute infectious diarrhea in children and adults, antibiotic-associated diarrhea, traveler's diarrhea, infant food allergies, vaccine adjuvants, dental caries, and acute respiratory infections.
It is common practice in commercial production of Lactobacillus probiotics to mix the bacterial strain with prebiotics such as oligofructose or inulin. Laboratory investigations, however, have established that these prebiotics are not well metabolized by LGG and therefore do not support the growth of this organism. It has also been shown that LGG cannot effectively metabolize other complex sugars such as oligoxylans, oligoarabinoxylans, and raffinose.